Percutaneous mechanical thrombectomy for acute pulmonary embolism: a double-edged sword

Percutaneous mechanical thrombectomy in patients with high-risk pulmonary embolism and contraindications for thrombolytic therapy

Background High-risk pulmonary embolism is associated with a high early mortality rate. We report our experience with percutaneous mechanical thrombectomy in patients with high-risk pulmonary embolism and contraindications for thrombolytic therapy. Patients and methods This was a retrospective analysis of consecutive patients with high-risk pulmonary embolism and contraindications to thrombolytic therapy. They were treated with percutaneous mechanical thrombectomy which included thrombectomy and additional thrombus aspiration when needed. Clinical parameters and survival to discharge were measured. Results From November 2005 to September 2015 we treated 25 patients with a mean age of 62.6 ± 12.7 years, 64% were men. Mean simplified Pulmonary Embolism Severity Index was 2.9. Mean maximum lactate levels were 7.8 ± 6.6 mmol/L, vasopressors were used in 77%, and 59% needed mechanical ventilation. Mechanical treatment included thrombus fragmentation complemented with aspiration (56%) and aspiration using Aspirex®S catheter (44%). Local (5 patients; 20%) and systemic (3 patients; 12%) thrombolytics were used as a salvage therapy. We observed nonsignificant improvements in systemic blood pressure (100 ± 41 mm Hg vs 119 ± 34; p = 0.100) and heart frequency (99 ± 35 min-1 vs 87 ± 31 min-1; p = 0.326) before and after treatment, respectively. Peak systolic tricuspid pressure gradient was significantly lower after treatment (57 ± 14 mm Hg vs 31 ± 3 mm Hg; p = 0.018). Overall the procedure was technically successful in 20 patients (80%) and 17 patients (68%) survived to hospital discharge. Conclusions In patients with high-risk pulmonary embolism who cannot receive thrombolytic therapy, percutaneous mechanical thrombectomy is a promising alternative to reduce pulmonary artery pressure.

Catheter-directed therapy as a treatment for submassive pulmonary embolism: A meta-analysis

AIMS

Catheter-directed therapy (CDT) is included in the guidelines for diagnosing and treating massive pulmonary embolism. However, few studies have evaluated the efficacy of CDT as a treatment for submassive pulmonary embolism (SPE). Therefore, we used evidence-based medicine to evaluate the effectiveness and safety of CDT in treating SPE.

METHODS

Search terms describing CDT in SPE and patients with intermediate pulmonary embolism were entered into the PubMed, Embase and Cochrane Library databases to identify relevant articles without language restrictions published between January 1990 and December 2016. A quality assessment and data extraction were performed by two investigators. The clinical efficacy of and major complications associated with treatment were analysed using a fixed effects model.

KEY FINDINGS

A total of 552 patients in 16 studies were included in this meta-analysis. The clinical success rate in CDT was approximately 100% (95% confidence interval (CI): 99%, 100%), the primary bleeding rate was 0.02% (95% CI: 0%, 0.05%), and mortality during hospitalization was approximately 0% (95% CI: 0%, 0.01%). The mean decrease in pulmonary artery systolic pressure after treatment was -14.9% (95% CI: -19.25%, -10.55%), and the mean post-treatment change in the ratio of the right to the left ventricle (RV/LV) was -0.35% (95% CI: -0.48%, -0.22%).

SIGNIFICANCE

CDT is effective and safe as a treatment for SPE and could be a first-line treatment for SPE under specific conditions.

A Prospective, Single-Arm, Multicenter Trial of Ultrasound-Facilitated, Catheter-Directed, Low-Dose Fibrinolysis for Acute Massive and Submassive Pulmonary Embolism: The SEATTLE II Study

OBJECTIVES

This study conducted a prospective, single-arm, multicenter trial to evaluate the safety and efficacy of ultrasound-facilitated, catheter-directed, low-dose fibrinolysis, using the EkoSonic Endovascular System (EKOS, Bothell, Washington).

BACKGROUND

Systemic fibrinolysis for acute pulmonary embolism (PE) reduces cardiovascular collapse but causes hemorrhagic stroke at a rate exceeding 2%.

METHODS

Eligible patients had a proximal PE and a right ventricular (RV)-to-left ventricular (LV) diameter ratio ≥0.9 on chest computed tomography (CT). We included 150 patients with acute massive (n = 31) or submassive (n = 119) PE. We used 24 mg of tissue-plasminogen activator (t-PA) administered either as 1 mg/h for 24 h with a unilateral catheter or 1 mg/h/catheter for 12 h with bilateral catheters. The primary safety outcome was major bleeding within 72 h of procedure initiation. The primary efficacy outcome was the change in the chest CT-measured RV/LV diameter ratio within 48 h of procedure initiation.

RESULTS

Mean RV/LV diameter ratio decreased from baseline to 48 h post-procedure (1.55 vs. 1.13; mean difference, -0.42; p < 0.0001). Mean pulmonary artery systolic pressure (51.4 mm Hg vs. 36.9 mm Hg; p < 0.0001) and modified Miller Index score (22.5 vs. 15.8; p < 0.0001) also decreased post-procedure. One GUSTO (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries)-defined severe bleed (groin hematoma with transient hypotension) and 16 GUSTO-defined moderate bleeding events occurred in 15 patients (10%). No patient experienced intracranial hemorrhage.

CONCLUSIONS

Ultrasound-facilitated, catheter-directed, low-dose fibrinolysis decreased RV dilation, reduced pulmonary hypertension, decreased anatomic thrombus burden, and minimized intracranial hemorrhage in patients with acute massive and submassive PE. (A Prospective, Single-arm, Multi-center Trial of EkoSonic® Endovascular System and Activase for Treatment of Acute Pulmonary Embolism (PE) [SEATTLE II]; NCT01513759).

Catheter-Directed Therapy in Acute Pulmonary Embolism with Right Ventricular Dysfunction: A Promising Modality to Provide Early Hemodynamic Recovery

BACKGROUND Catheter-directed therapy (CDT) for pulmonary embolism (PE) is considered as an alternative to systemic thrombolysis (ST) in patients with hemodynamically unstable acute PE who are considered at high bleeding risk for ST. We aimed to evaluate the efficacy and safety of CDT in the management of acute PE with right ventricular dysfunction (RVD). The primary outcomes were mortality, clinical success, and complications. Secondary outcomes were change in hemodynamic parameters in the first 24 hours following the procedure. MATERIAL AND METHODS Medical records of consecutive patients diagnosed as having acute massive or submassive PE with accompanying RVD treated by immediate CDT at our institution from January 2007 to January 2014 were reviewed. Patient characteristics, mortality, achievement of clinical success, and minor and major bleeding complications were analyzed in the overall study group, as well as massive vs. submassive PE subgroups. Change in hemodynamic parameters in the second, eighth, and 24th hours after the CDT procedure were also analyzed. RESULTS The study included 15 consecutive patients (M/F=10/5) with a mean age of 54.2 ± 16.6 years who underwent immediate CDT. Nine of the patients had submassive PE, and 6 had massive PE. In-hospital mortality rate was 13.3% (95% CI, 0.04-0.38). One major, but not life-threatening, bleeding episode was evident in the whole group. Hemodynamic parameters were stabilized and clinical success was achieved in 14/15 (93.3%; 95% CI, 70.2-98.8) of the patients in the first 24 hours. Notably, the hemodynamic recovery was significantly evident in the first 8 hours after the procedure. CONCLUSIONS CDT is a promising treatment option for patients with acute PE with RVD with no fatal bleeding complication. In experienced centers, CDT should be considered as a first-line treatment for patients with acute PE and RVD and contraindications for ST, with the advantage of providing early hemodynamic recovery.

Guidance for the use of thrombolytic therapy for the treatment of venous thromboembolism

Patients with venous thromboembolism (VTE) are prone to the development of both short-term and long-term complications that can substantially affect their functional capacity and quality of life. Patients with deep vein thrombosis (DVT) often develop recurrent VTE or the post-thrombotic syndrome, whereas patients with pulmonary embolism (PE) can develop long-term symptoms and functional limitations along a broad spectrum extending to full-blown chronic thromboembolic pulmonary hypertension. Clinicians who care for patients showing severe clinical manifestations of DVT and PE are often faced with challenging decisions concerning whether and how to escalate to more aggressive treatments such as those involving the use of thrombolytic drugs. The purpose of this chapter is to provide guidance on how best to individualize care to these patients.

Pulmonary Embolism Response to Fragmentation, Embolectomy, and Catheter Thrombolysis (PERFECT): Initial Results From a Prospective Multicenter Registry

BACKGROUND

Systemic thrombolysis for acute pulmonary embolism (PE) carries up to a 20% risk of major bleeding, including a 2% to 5% risk of hemorrhagic stroke. We evaluated the safety and effectiveness of catheter-directed therapy (CDT) as an alternative treatment of acute PE.

METHODS

One hundred one consecutive patients receiving CDT for acute PE were prospectively enrolled in a multicenter registry. Massive PE (n = 28) and submassive PE (n = 73) were treated with immediate catheter-directed mechanical or pharmacomechanical thrombectomy and/or catheter-directed thrombolysis through low-dose hourly drug infusion with tissue plasminogen activator (tPA) or urokinase. Clinical success was defined as meeting all the following criteria: stabilization of hemodynamics; improvement in pulmonary hypertension, right-sided heart strain, or both; and survival to hospital discharge. Primary safety outcomes were major procedure-related complications and major bleeding events.

RESULTS

Fifty-three men and 48 women (average age, 60 years [range, 22-86 years]; mean BMI, 31.03 ± 7.20 kg/m2) were included in the study. The average thrombolytic doses were 28.0 ± 11 mg tPA (n = 76) and 2,697,101 ± 936,287 International Units for urokinase (n = 23). Clinical success was achieved in 24 of 28 patients with massive PE (85.7%; 95% CI, 67.3%-96.0%) and 71 of 73 patients with submassive PE (97.3%; 95% CI, 90.5%-99.7%). The mean pulmonary artery pressure improved from 51.17 ± 14.06 to 37.23 ± 15.81 mm Hg (n = 92) (P < .0001). Among patients monitored with follow-up echocardiography, 57 of 64 (89.1%; 95% CI, 78.8%-95.5%; P < .0001) showed improvement in right-sided heart strain. There were no major procedure-related complications, major hemorrhages, or hemorrhagic strokes.

CONCLUSIONS

CDT improves clinical outcomes in patients with acute PE while minimizing the risk of major bleeding. At experienced centers, CDT is a safe and effective treatment of both acute massive and submassive PE.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01097928; URL: www.clinicaltrials.gov.

Experimental model of large pulmonary embolism employing controlled release of subacute caval thrombus in swine

PURPOSE

To develop a catheter-based model of large pulmonary embolism (PE) in swine based on in situ venous thrombus formation.

MATERIALS AND METHODS

Ten Yorkshire swine underwent transjugular implantation of a retrievable inferior vena cava (IVC) filter. A thrombin and collagen mixture was injected into a confined space created by two balloons inflated proximal and distal to the IVC filter. Animals were left to survive for 7 days ± 3 to allow thrombus to organize in situ. The caval thrombus was released on transcatheter retrieval of the IVC filter and embolized into the main and branch pulmonary arteries. The severity of PE was scored based on digital subtraction angiography with the Miller index. At necropsy, thrombi were recovered and analyzed histopathologically.

RESULTS

Large PE was induced in all animals (Miller index score of 15 ± 5). Two animals developed saddle embolus with bilateral pulmonary artery occlusion, and five developed proximal occlusion of the left or right pulmonary artery. Nevertheless, no animal exhibited significant hemodynamic compromise. Large tubular thrombi were explanted in the size range of 5-10 cm long and 0.5-1 cm wide. Histologic analysis indicated an organized thrombus with infiltration of white blood cells and fibrin deposition.

CONCLUSIONS

Large caval thrombi can be formed in vivo and released at a predetermined time to induce large PE in a large animal model. This may help in the development and testing of new therapeutic approaches for PE.

Diagnosis and management of life-threatening pulmonary embolism

Pulmonary embolus (PE) is estimated to cause 200 000 to 300 000 deaths annually. Many deaths occur in hemodynamically unstable patients and the estimated mortality for inpatients with hemodynamic instability is between 15% and 25%. The diagnosis of PE in the critically ill is often challenging because the presentation is nonspecific. Computed tomographic pulmonary angiography appears to be the most useful study for diagnosis of PE in the critically ill. For patients with renal insufficiency and contrast allergy, the ventilation perfusion scan provides an alternative. For patients too unstable to travel, echocardiography (especially transesophageal echocardiography) is another option. A positive result on lower extremity Doppler ultrasound can also aid in the decision to treat. The choice of treatment in PE depends on the estimated risk of poor outcome. The presence of hypotension is the most significant predictor of poor outcome and defines those with massive PE. Normotensive patients with evidence of right ventricular (RV) dysfunction, as assessed by echocardiography, comprise the sub-massive category and are at intermediate risk of poor outcomes. Clinically, those with sub-massive PE are difficult to distinguish from those with low-risk PE. Cardiac troponin, brain natriuretic peptide, and computed tomographic pulmonary angiography can raise the suspicion that a patient has sub-massive PE, but the echocardiogram remains the primary means of identifying RV dysfunction. The initial therapy for patients with PE is anticoagulation. Use of vasopressors, inotropes, pulmonary artery (PA) vasodilators and mechanical ventilation can stabilize critically ill patients. The recommended definitive treatment for patients with massive PE is thrombolysis (in addition to anticoagulation). In massive PE, thrombolytics reduce the risk of recurrent PE, cause rapid improvement in hemodynamics, and probably reduce mortality compared with anticoagulation alone. For patients with a contraindication to anticoagulation and thrombolytic therapy, surgical embolectomy and catheter-based therapies are options. Thrombolytic therapy in sub-massive PE results in improved pulmonary perfusion, reduced PA pressures, and a less complicated hospital course. No survival benefit has been documented, however. If one is considering the use of thrombolytic therapy in sub-massive PE, the limited documented benefit must be weighed against the increased risk of life-threatening hemorrhage. The role of surgical embolectomy and catheter-based therapies in this population is unclear. Evidence suggests that sub-massive PE is a heterogeneous group with respect to risk. It is possible that those at highest risk may benefit from thrombolysis, but existing studies do not identify subgroups within the sub-massive category. The role of inferior vena cava (IVC) filters, catheter-based interventions, and surgical embolectomy in life-threatening PE has yet to be completely defined.

Fibrinolysis for acute pulmonary embolism

Acute pulmonary embolism (PE) presents as a constellation of clinical syndromes with a variety of prognostic implications. Patients with acute PE who have normal systemic arterial blood pressure and no evidence of right ventricular (RV) dysfunction have an excellent prognosis with therapeutic anticoagulation alone. Normotensive acute PE patients with evidence of RV dysfunction are categorized as having submassive PE and comprise a population at intermediate risk for adverse events and early mortality. Patients with massive PE present with syncope, systemic arterial hypotension, cardiogenic shock, or cardiac arrest and have the highest risk for short-term mortality and adverse events. The majority of deaths from acute PE are due to RV pressure overload and subsequent RV failure. The goal of fibrinolysis in acute PE is to rapidly reduce RV afterload and avert impending hemodynamic collapse and death. Although generally considered to be a life-saving intervention in massive PE, fibrinolysis remains controversial for submassive PE. Successful administration of fibrinolytic therapy requires weighing benefit versus risk. Major bleeding, in particular intracranial hemorrhage, is the most feared complication of fibrinolysis. Alternatives to fibrinolysis for acute PE, including surgical embolectomy, catheter-assisted embolectomy, and inferior vena cava (IVC) filter insertion, should be considered when contraindications exist or when patients have failed to respond to an initial trial of fibrinolytic therapy. Patients with massive and submassive PE may be best served by rapid triage to specialized centers with experience in the administration of fibrinolytic therapy and the capacity to offer alternative advanced therapies such as surgical and catheter-assisted embolectomy.

Catheter-directed therapy for the treatment of massive pulmonary embolism: systematic review and meta-analysis of modern techniques

PURPOSE

Systemic thrombolysis for the treatment of acute pulmonary embolism (PE) carries an estimated 20% risk of major hemorrhage, including a 3%-5% risk of hemorrhagic stroke. The authors used evidence-based methods to evaluate the safety and effectiveness of modern catheter-directed therapy (CDT) as an alternative treatment for massive PE.

MATERIALS AND METHODS

The systematic review was initiated by electronic literature searches (MEDLINE, EMBASE) for studies published from January 1990 through September 2008. Inclusion criteria were applied to select patients with acute massive PE treated with modern CDT. Modern techniques were defined as the use of low-profile devices (< or =10 F), mechanical fragmentation and/or aspiration of emboli including rheolytic thrombectomy, and intraclot thrombolytic injection if a local drug was infused. Relevant non-English language articles were translated into English. Paired reviewers assessed study quality and abstracted data. Meta-analysis was performed by using random effects models to calculate pooled estimates for complications and clinical success rates across studies. Clinical success was defined as stabilization of hemodynamics, resolution of hypoxia, and survival to hospital discharge.

RESULTS

Five hundred ninety-four patients from 35 studies (six prospective, 29 retrospective) met the criteria for inclusion. The pooled clinical success rate from CDT was 86.5% (95% confidence interval [CI]: 82.1%, 90.2%). Pooled risks of minor and major procedural complications were 7.9% (95% CI: 5.0%, 11.3%) and 2.4% (95% CI: 1.9%, 4.3%), respectively. Data on the use of systemic thrombolysis before CDT were available in 571 patients; 546 of those patients (95%) were treated with CDT as the first adjunct to heparin without previous intravenous thrombolysis.

CONCLUSIONS

Modern CDT is a relatively safe and effective treatment for acute massive PE. At experienced centers, CDT should be considered as a first-line treatment for patients with massive PE.

Combined clot fragmentation and aspiration in patients with acute pulmonary embolism

BACKGROUND

Massive angiographic pulmonary embolism (PE) with right ventricular dysfunction (RVD) is associated with a high early mortality rate. The therapeutic alternatives for this condition include thrombolysis, surgical embolectomy, or percutaneous mechanical thrombectomy (PMT). We describe our experience using PMT in patients with massive PE and RVD with unsuccessful thrombolysis, increased bleeding risk, or major contraindications for thrombolytic therapy.

METHODS

Clinical, hemodynamic, and angiographic parameters prior to and following PMT were evaluated. Our primary objective was to describe the incidence of in-hospital cardiovascular death, and of major and minor complications. Mid-term outcomes included analysis of occurrence of cardiovascular death, recurrent pulmonary embolism, change of New York Heart Association functional class, and hospital readmission.

RESULTS

From July 2004 to May 2007, 69 patients were referred to the cardiac catheterization laboratory with a diagnosis of acute PE, 18 of whom met the criteria for massive PE and are the subject of this study. All patients underwent thrombus fragmentation using a pigtail catheter that was complemented in 13 patients with thrombus aspiration. A percutaneous thrombectomy device (Aspirex; Straub Medical; Wangs, Switzerland) was used in 11 patients. Hemodynamic, angiographic, and blood oxygenation parameters improved after the procedure. A significant increase was observed for systolic systemic BP (74.3+/-7.5 mm Hg vs 89.4+/-11.3 mm Hg, p=0.001) [mean+/-SD], as was a decrease in mean pulmonary artery pressure (37.1+/-8.5 mm Hg vs 32.3+/-10.5 mm Hg , p=0.0001). The in-hospital major complications rate was 11.1%; one patient died from refractory shock, and one patient had intracerebral hemorrhage with minor neurologic sequelae. No cardiovascular deaths or recurrent pulmonary thromboembolism were documented during clinical follow-up (12.3+/-9.4 months).

CONCLUSIONS

In patients with massive PE, RVD and major contraindications to thrombolytic therapy, increased bleeding risk, failed thrombolysis, or unavailable surgical thrombectomy, PMT appears to be a useful therapeutic alternative.